This invention relates, in general, to memory arrays, and more particularly, to a memory array having a reference voltage generator for use with multi-state memory cells of the memory array.
Memory arrays of the past typically contain memory cells which are capable of storing one or the other of two states. These type of memory arrays did not require an elaborate reference voltage generator since only one of two states was expected to be found in a given memory storage location. A memory having storage locations capable of storing more than two states requires some way of determining which of the multiple states is stored in a given storage location. A voltage reference would be useful in a memory array having memory cells which store more than two states in the form of a voltage level.
Accordingly, it is an object of the present invention to provide a memory array having a reference voltage generator all on the same chip with a plurality of memory cells capable of storing more than two states.
Another object of the present invention is to provide a reference voltage generator for a read only memory which is useful for determining a voltage level stored within a memory cell of the memory.
Yet another object of the present invention is to provide a memory having a reference voltage generator and a comparator for comparing the difference between the reference voltage generator and a voltage level from a memory cell capable of storing more than two states.
Yet a further object of the present invention is to provide a reference signal which is generated in the same manner as a signal to be identified whereby wide processing variations can be tolerated since the reference signal will track the unknown signal very closely.